Many polyacetylenic compounds form a colored polymer on exposure to radiation and are therefore useful in photography. The use of these compounds has been limited however because of their low sensitivity. Further, many of these compounds which are otherwise desirable, are sensitive only to ultraviolet radiation. As a result of these drawbacks, there has been much effort to improve both the spectral sensitivity and overall sensitivity of processes using polyacetylenic compounds. Thus, in U.S. Pat. No. 3,501,308 to Albert H. Adelman, issued Mar. 17, 1970, the spectral sensitivity of polyacetylenic compounds is extended towards or into the visible region by the presence of an organic .pi.-acid electron acceptor. In another patent, U.S. Pat. No. 3,794,491 to Paul M. Borsenberger et al issued Feb. 26, 1974, a process for amplifying existing polyacetylenic images is disclosed. A weak image is first formed in the layer by exposure of the layer to radiation to which the polyacetylenic compound is sensitive. The weak image is then amplified by exposing the layer to uniform radiation which is preferentially absorbed by the preformed weak image areas. This process amplifies an existing image and does not alter the spectral sensitivity of the polyacetylenic material.
Several other processes have been suggested which use the polymerization of a polyacetylenic compound to form an image. In U.S. Pat. No. 3,772,011, Paul M. Borsenberger et al describe a process wherein a polyacetylenic compound undergoes imagewise polymerization when contiguous to a photoconductive layer. The photoconductive layer is exposed during the application of an electric potential across the polyacetylenic layer and the photoconductive layer. Borsenberger et al believe that the direct polymerization is a result of charge carriers, ions or free radicals being injected into the polyacetylenic layer from the photoconductor. As a result, the spectral and overall sensitivity of this process may be altered by adding sensitizers to the photoconductive layer. In U.S. Pat. No. 3,726,769, Borsenberger et al. describe a process wherein an image is formed in a polyacetylenic compound containing layer by means of selective arcing adjacent to the surface of the polyacetylenic layer. The image in the polyacetylenic layer is thus formed by a concentrated imagewise electrical potential that is generated between an electrode closely spaced to a sensitive polyacetylenic layer having a conductive backing.
Since polyacetylenic compounds are relatively inexpensive, there is a continuing need for a process using polyacetylenic compounds which have improved sensitivity. It would also be desirable to have a process and element which is capable of recording more than one portion of the electromagnetic spectrum.